In an exemplary wireless communications network, each wireless device may communicate via an air interface with a base transceiver station (“BTS”) and in turn with a base station controller (“BSC”). The BSC may then be coupled with a mobile switching center (“MSC”). Further, the BSC may be coupled with a packet data serving node (“PDSN”) or other gateway, which may provide connectivity with an IP network, such as the public Internet or a private intranet (e.g., a wireless carrier's core IP network). The wireless device may thus communicate with entities on the IP network via communication path comprising the air interface, the BTS, the BSC and the PDSN.
A properly equipped wireless device can initiate packet-data communication by sending an initiation request message over an air interface signaling channel, and via the BSC, to the MSC. Applying industry standards, the initiation request message may include a “packet data” service option code that characterizes the requested communication as packet-data communications, as compared with traditional voice communication. When the MSC receives the initiation request, it may then detect the “packet data” service option code and responsively send the message back to the BSC for handling.
In turn, when the BSC receives the initiation request from the MSC, the BSC may establish a radio link layer connection with the wireless device, by assigning the wireless device to operate on a particular traffic channel over the air interface (e.g., a fundamental traffic channel, and perhaps one or more supplemental channels). In addition, the BSC may pass the initiation request to the PDSN. The PDSN and the wireless device may then negotiate with each other to establish a data-link layer connection, typically a point-to-point session (“PPP”) over which packet data can be communicated between the wireless device and the PDSN.
In most wireless communication systems like this, the radio-link layer connection with the wireless device may time-out after a predefined period of inactivity. For instance, after ten seconds in which no data is communicated to or from the wireless device over the air interface, the BSC may release the traffic channel that had been assigned to the wireless device. At the same time, however, the data-link layer (e.g., PPP) connection with the wireless device might remain.
Once the radio-link layer connection with the wireless device has timed out, the wireless device will be considered “dormant.” However, if its data-link layer connection still exits, the wireless device may still seek to send packet data to other entities, and other entities may seek to send packet data to the wireless device. When another entity seeks to send packet data to the wireless device, the BSC will page the wireless device over a signaling channel.
When the wireless device seeks to send data, for example in order to establish a session with a second device, such as a wireless device or a wired device, the radio link layer connection with the wireless device will need to be reestablished. To do so, the wireless device may send a message to the BSC over the signaling channel requesting radio-link resources, and the BSC may then assign a traffic channel to the wireless device. Then the wireless device can use the traffic channel to communicate with the second device. For example, the wireless device may then send a request to establish a session, such as a Session Initiation Protocol (“SIP”) INVITE message, to the second device via the traffic channel.
If the second device is also a wireless device, it may also be in the dormant state, in which case a BSC for the second device would need to establish a traffic channel with the second device before forwarding to it the SIP INVITE message. After receiving the SIP INVITE message via the established traffic channel with the BSC, the second device could then respond to the message, such as by sending the first wireless device a SIP OK message via the established traffic channels.
This process, however, introduces a latency in establishing the session. Before sending a request to establish a session, the first wireless device establishes a traffic channel with its BSC, which can take on the order of 2-3 seconds. Similarly, if the second device is also a wireless device, it may establish a traffic channel before receiving the request. This can also take on the order of 2-3 seconds. Thus, merely establishing the traffic channels may introduce a latency of approximately 2-3 seconds in a session involving one wireless device, and a latency of approximately 4-6 seconds in a session involving two wireless devices. It should be understood that these times are exemplary in nature and may vary depending on the type of wireless network and on other factors.
The latency can be noticeable, for example, to a wireless device user establishing a session between the two wireless devices in order to place a voice call, such as may be done by using the Voice over Internet Protocol (“VoIP”) to send voice traffic over a packet-data connection.
Therefore, there exists a need for an improved method of call setup in a wireless telecommunications network.